Locking Unit with Centre Piece

ABSTRACT

The invention relates to a locking unit, in particular for the parking lock of an automatic transmission, for locking the movement of a piston which is movable by a drive and in particular can be acted upon with pressure or hydraulic pressure, wherein the piston is at least partially mounted in a center section which is at least partially surrounded by a housing.

The invention relates to a locking unit, in particular for the parkinglock of an automatic transmission, for locking the movement of a pistonwhich is movable by a drive and in particular can be acted upon withpressure or hydraulic pressure, the locking unit having a solenoid andat least one latching element, and the latching element interacting withthe armature or the armature rod of the solenoid, and the piston havingat least one latching receptacle, and the piston being securable by theretaining interaction of the latching element with the latchingreceptacle.

A locking unit of the type in question is known, for example, from theapplicant's international patent application WO 2013/131926.

It is an object of the invention to design a known locking unit in analternative or better manner. This is achieved according to theinvention by a locking unit as claimed in claim 1. Advantageousembodiments can be gathered, for example, from the dependent claims.

The invention relates to a locking unit, in particular for the parkinglock of an automatic transmission, for locking the movement of a pistonwhich is movable by a drive and in particular can be acted upon withpressure or hydraulic pressure, the locking unit having a solenoid andat least one latching element, and the latching element interacting withthe armature or the armature rod of the solenoid, and the piston havingat least one latching receptacle, and the piston being securable by theretaining interaction of the latching element with the latchingreceptacle.

According to the invention, it is provided that the piston is at leastpartially mounted in a center section which is at least partiallysurrounded by a housing, and the locking unit has a latching unit, whichsupports the latching elements, wherein the latching unit and the centersection (6) are formed integrally. It has been shown that this leads toan advantageous operation, permits a high degree of stability and issimple to manufacture.

The center section can in particular be designed in the manner of asleeve.

An inner side of the center section preferably forms a bearing surfacefor the piston or for a piston thrust piece of the piston. The pistoncan thereby be advantageously mounted.

The center section can be in the form in particular of a turned part orsintered shaped part, can be produced in a formative method or can beproduced by means of 3D printing, metal powder injection molding,selective laser melting or selective laser sintering. Such methods haveproven advantageous. However, other methods are also possible.

The center section preferably has an axial length of 100% to 200% or of130% to 170% of a stroke of the piston.

The center section furthermore preferably has an axial length of 30% to40% of an axial length of the piston.

The center section furthermore preferably has an axial length of 13% to20% of an axial length of the locking unit.

According to a preferred embodiment, it is provided that the piston ishollow on the inside completely along its axial extent. Weight canthereby be saved.

In particular, it can be provided that the piston has a cavity whichextends axially though the entire piston.

The cavity is preferably open at both axial ends.

It is preferably provided that the cavity has a wall continuously or insections which is thinner than a quarter of a diameter of the piston oris thinner than a tenth of the diameter of the piston.

According to a preferred embodiment, it is provided that the piston hasa completely hollow piston tube along one axial portion and a pistonthrust piece, which is connected to the piston tube, along a furtheraxial portion. As a result, piston tube and piston thrust piece can beoptimized separately from each other in accordance with their respectivefunctions.

The latching receptacles are preferably formed in the piston thrustpiece. The piston thrust piece is preferably closer to the solenoid andmore solid than the piston tube.

The piston tube can be in the form in particular of a deep drawn part,from tool steel or from metal. However, other embodiments are alsopossible.

According to a preferred embodiment, it is provided that the piston tubehas a wall thickness of 5% to 15% of the diameter of the piston tube.

It is preferably provided that the piston is at least partially mountedor arranged in the housing.

According to a preferred embodiment, it is provided that the housing isat least partially, preferably completely, formed from plastic. This hasproven advantageous, in particular because of the easy processabilityand the low weight. However, other materials are also possible.

The piston tube preferably has a tube center section with an outertapering, wherein the tapering of the piston tube interacts with a stepformed in the housing, in order to limit a movement of the piston awayfrom the solenoid. Said movement can thereby be limited simply andreliably.

In particular, a piston spring can be provided between housing andpiston, said piston spring pushing the piston in the direction of thesolenoid. The piston can thereby be pretensioned into an inoperativeposition which it takes up in particular in the absence of an activeactuation, i.e., for example, in the absence of a pressurized fluid andif blocking is absent.

According to a preferred embodiment, it is provided that the piston ismounted opposite the solenoid in a plain bearing of the housing. Thispermits reliable guidance of the piston.

The housing or the locking unit can have in particular an inner tubesection.

The inner tube section can be considered in general to be part of thelocking unit or part of the housing.

In particular a pressure conducting channel can be formed on the outerside of the tube section. A pressurized medium can flow into saidpressure conducting channel in order to actuate the piston. For example,by means of a tightness, described further below, between tube sectionand housing, the medium can advantageously be conducted to a position atwhich it is required for driving the piston.

The pressure conducting channel is preferably hydraulically connectablefrom the outside via a connection through the housing. This makes itpossible to supply pressurized fluid.

The center section preferably has a radial outer side which supports thehousing. This permits a reliable connection between housing and centersection.

The center section can be connected in particular to a solenoid housingof the solenoid. This permits a secure reference between the twocomponents.

The center section can have an encircling contact shoulder on its sidefacing away from the solenoid and/or facing the piston tube, whichcontact shoulder is adjoined by an annular and/or conical connectingregion.

According to a preferred embodiment, it is provided that the connectingregion supports the tube section. The tube section can thereby bereliably fastened.

A number of segment interspaces as notches can be formed in theconnecting region, in particular radially on the outer side. As aresult, for example, a passage of fluid can be made possible.

The segment interspaces are preferably designed as a fluidic connectionbetween pressure conducting channel and a pressure space within the tubesection. This makes it possible to conduct pressure out of the pressureconducting channel into the pressure space.

Respective supporting segments which support the tube section can beformed between the segment interspaces. This permits a secure connectionto the tube section. The connecting region can be designed in particularas a crown ring.

According to a preferred embodiment, it is provided that the lockingunit has a latching unit which supports the latching elements.

The latching unit can have in particular a portion facing the solenoidor an armature space of the solenoid and a portion facing the piston,which portions are both of sleeve-shaped design.

It is preferably provided that that portion of the latching unit whichfaces the solenoid partially accommodates the armature in at least oneend position.

An interior space which is open on the piston side is preferably formedin the latching unit or in that portion of the latching unit which facesthe piston.

An exterior space can be formed between latching unit and housing orbetween latching unit and center section.

Exterior space and interior space can be fluidically connected inparticular via an equalizing opening formed in the latching unit. Thiscan permit an equalization of the pressure.

It is preferably provided that the exterior space is vented by a channelwhich is formed in or on the center section. The exterior space canthereby be kept at ambient pressure. The interior space can thereforealso be kept at ambient pressure by means of the equalizing openingwhich has already been mentioned.

The latching unit is preferably fixedly connected directly or indirectlyto the housing. This permits a constant positional relationship.

In particular a control element which is fixedly connected to thearmature rod can be arranged in the latching unit. Said control elementcan serve in particular for actuating the latching elements.

The control element is preferably at least partially movable within theportion facing the piston.

According to a preferred embodiment, it is provided that a number ofradial bores for receiving the latching elements is formed in thelatching unit. The latching elements can thereby be reliably guided.

The latching elements can in particular be formed spherically. However,other shapes are also possible.

The control element can preferably be designed in order, at least in oneposition, to push the latching elements radially outward. They canthereby deploy a blocking effect.

It is preferably provided that the latching elements, when they arepushed radially outward, come into engagement with one of the latchingreceptacles. As a result, they can block a movement of the piston.

The piston preferably has at least two latching receptacles spaced apartaxially from one another. This permits blocking of the piston in atleast two positions. However, the use of more than two latchingreceptacles is also possible.

The piston is furthermore preferably lockable in two different positionsby means of the two latching receptacles. Accordingly, if there are morethan two latching receptacles, it is also possible for there to belocking in more than two positions.

The solenoid can have in particular a solenoid core which is arranged atan axial end of the locking device.

The armature rod is preferably guided in a bore of the solenoid core.This permits reliable guidance of the armature rod.

The piston preferably has an axially end-side connecting region whichprotrudes out of the housing even when the piston is fully retracted.This permits a simple connection of an external element to the piston.

The connecting region can be designed in particular in the manner of afork. This permits an advantageous fastening of typical externalelements. The connecting region can also be designed as a punched-outfork head.

According to a preferred embodiment, it is provided that the piston orthe piston thrust piece is at least partially arranged radially betweenlatching unit and housing or is arranged between latching unit andcenter section.

The solenoid preferably has a winding for generating a magnetic fieldfor moving the armature and/or the armature rod. This permits a simpleactuation.

The inner tube section is preferably designed as a guide of the piston.The guide on the tube section achieves particularly good guidance of thepiston, and therefore the latter can be moved in as smooth-running amanner as possible.

The pressure conducting channel is preferably limited at least partiallyradially, with respect to the longitudinal axis of the piston, on theinside by the outer side of the tube section and on the outside by theinner wall of the housing.

The tube section can be connected to the housing or can be part of thehousing.

The piston preferably lies against the tube section. This permitsparticularly advantageous guidance of the piston along the tube section.The contact can take place along a full circumference.

It is preferably provided that the piston slides along the tube section.

According to a preferred embodiment, the piston lies in a fluid-tightmanner against the tube section. The piston can thereby beadvantageously actuated by pressure.

The piston preferably has a sealing means which seals the piston in afluid-tight manner on the tube section. This permits a particularlyleakproof design.

The sealing means can be, for example, a sealing ring or an O ring. Thesealing ring or the O ring can be provided in particular in anencircling step of the piston.

The sealing ring or the O ring is preferably provided in a piston thrustpiece of the piston.

The inner side of the tube section preferably forms a housing inner wallagainst which the piston lies.

The tube section is preferably of rectilinear and/or cylindrical designat least along a portion on which the piston is guided. This permits anadvantageous interaction with the piston.

The tube section is preferably formed from metal or from plastic. Thesematerials have proven advantageous. However, the use of other materialsis also possible.

According to a preferred embodiment, it is provided that the centersection is designed in the axial direction, with respect to thelongitudinal axis of the piston, to be shorter on the piston side thanthe latching unit and in particular the radial bores of the latchingunit are not concealed in the radial direction, with respect to thelongitudinal axis of the piston, by the center section.

According to a preferred embodiment, it is provided that the inner tubesection is connected in a fluid-tight manner to the housing.

The effect which can be achieved in an advantageous manner by such afluid-tight embodiment is that leakage between tube section and housingis prevented. Such leakage could lead, for example, to pressurized fluidescaping into a space in which it could prevent the movement of thepiston.

According to a preferred embodiment, it is provided that the tubesection is accommodated in a groove of the housing. This makes reliableholding possible.

The groove of the housing can be of in particular annular design. It cantherefore be advantageously adapted to a cylindrical tube section.

According to a preferred embodiment, it is provided that a seal isarranged between housing and tube section. A sealing effect cantherefore be advantageously achieved.

The seal can be arranged in particular in the groove. It can be an Oring or sealing ring. The seal can also be a sealing material or asilicone sealing material. Such embodiments have proven advantageous.

According to a preferred embodiment, it is provided that a number ofbores in which engagement parts of the housing engage is formed in thetube section. An advantageous fastening and/or sealing can thereby beachieved. The engagement parts can be formed in particular in aninternally bonded manner with the rest of the housing. They can beproduced, for example, by insert molding of the tube section duringproduction of the housing.

According to a preferred embodiment, it is provided that the housing hasan in particular annular projection which partially engages around thetube section. The tube section can therefore be advantageously held andalso sealed.

The projection can limit the groove in particular radially on the innerside.

According to a preferred embodiment, it is provided that the tubesection is connected to the housing in a gas-tight and/or pressure-tightmanner. Tightness going beyond the fluid tightness can thereby beachieved.

According to one embodiment, the housing can support the tube section.This permits an exact positional relationship between tube section andhousing.

According to one embodiment, latching unit and center section can beproduced or formed integrally as an integral injection molded part or inan additive manufacturing method. A number of radial recesses, inparticular bores, can therefore also be formed in the latching unit forreceiving the latching elements.

Center section and latching unit can be formed in particular integrally.The center section can be designed in the axial direction, with respectto the longitudinal axis of the piston, to be shorter on the piston sidethan the latching unit. In particular, it can be provided that theradial bores of the latching unit are not concealed in the radialdirection, with respect to the longitudinal axis of the piston, by thecenter section. This permits formation of the bores by tools, such asdrills, which can be guided past the center section.

The invention furthermore relates to a method for producing a lockingunit according to the invention, wherein the tube section is providedand the housing is insert molded around the tube section. By means ofsuch a method, the housing can be produced and connected to the tubesection in a simple manner. With regard to the locking unit, recoursecan be made to all of the embodiments and variants described herein.

According to an alternative method procedure, a groove into which thetube section is introduced subsequently can be formed in the housing.

A number of bores can be formed in the tube section, wherein a number ofengagement parts which each engage in a bore have been or are formed inthe housing. This permits a reliable connection. The engagement partscan be formed in particular in a materially bonded manner with the restof the housing.

For example, it can be provided that the piston is hollow on the inside.

The piston according to the aforementioned prior art is a complicatedturned part which is produced in a production process comprising aplurality of different machining steps. An essential aspect of a hollowdesign is focused on producing the individual components in simpleproduction methods. The proposed piston can be provided as a deep drawnpart in which the relatively complex contour of said piston is realizedin one processing step. In addition to the significantly more favorableproduction, the mass of such a piston can be reduced at the same time,which overall reduces the mass of the locking unit proposed according tothe invention, which firstly saves on resources and secondly alsopermits the drives which are to be used to be realized in smaller form,with the same dynamic properties, and thus also to be morecost-effective and also lighter.

According to one embodiment, it can also be provided that the piston isat least partially mounted in a housing which is at least partiallyformed from plastic.

The housing according to the aforementioned prior art is also acomplicated, cylindrical metal turned part, the inner side of which ismanufactured with high precision.

In the embodiment proposed herein, the housing can be composed, forexample, of plastic, wherein the plastic, for example, is sprayed ontothe structure, or the housing is kept as a finished injection moldedcomponent in which the individual parts of the locking unit according tothe invention are then installed. The proposal according to theinvention comprises in this case both a direct mounting of the piston onthe plastic, wherein then, for example, the inner side of the plasticshousing can have a corresponding wear-reducing sliding configuration,such as, for example, a sliding coating or the like, and also anindirect mounting of the piston in the housing formed from plastic. Forexample, in the case of the indirect mounting in the plastics housing, acorresponding guide sleeve, preferably composed of metal, or a guidetube can thus be provided, the inner side of which interacts with theouter side of the piston.

The plastics housing which can be realized as an injection molded partor as an insert molded part can be produced more simply and thereforemore cost-effectively than the submissions from the prior art. Theproposal is also not only limited here to the more favorable manner ofproduction, but in turn reduces the mass of the entire locking unitsince a lighter material is used for the housing.

It can also be provided that the piston is at least partially mounted ina center section which is at least partially surrounded by a housing.

This variant has the advantage that the piston is first of all guidedonly on the center section. A guide in the housing can be dispensed withhere, but it may also be additionally provided. According to thisproposal, the housing can be a component which is separate from thecenter section and can then be optimized in accordance with otheraspects since it, for example, no longer primarily has the task ofsupporting the piston. Since the housing is relatively large, it canthen be manufactured from a lighter material (e.g. plastic) than thematerial of the center section which takes on the supporting tasks andtherefore is preferably composed, for example, of a correspondingmetallic bearing material.

In a preferred refinement of the proposal, it is provided that thepiston is divided in two and has a hollow, for example deep drawn,piston tube and a piston thrust piece designed, for example, as a turnedpart.

In a preferred refinement of the proposal, it is provided that thepiston, in particular the piston tube, is of fork-like design at itsouter end.

In a preferred refinement of the proposal, it is provided that thepiston, preferably the piston thrust piece, has two latching receptacleswhich are offset axially with respect to each other.

In a preferred refinement of the proposal, it is provided that at leastpart of the piston, preferably the entire piston, is designed as a deepdrawn part.

In a preferred refinement of the proposal, it is provided that thehousing which is manufactured from plastic includes or surrounds asleeve section or tube section.

In a preferred refinement of the proposal, it is provided that the outerside of the tube section limits a pressure conducting channel.

In a preferred refinement of the proposal, it is provided that thesleeve section or tube section is placed or pressed onto a centersection.

In a preferred refinement of the proposal, it is provided that the innerside of the sleeve section or tube section forms a mounting for thepiston or the piston tube.

In a preferred refinement of the proposal, it is provided that a ventingchannel is provided on the center section, preferably on the side facingthe solenoid.

In a preferred refinement of the proposal, it is provided that thepiston spring is located within or outside the center part.

In a preferred refinement of the proposal, it is provided that thecenter section is in the form of a sintered shaped part or ismanufactured in a formative method, in particular by means of 3Dprinting, metal powder injection molding, selective laser melting orselective laser sintering. Sintering or formative manufacturing arecost-effective production methods with which, in addition, workpieces ofvirtually any shape can be produced in a single working cycle.

In a preferred refinement of the proposal, it is provided that thecenter part permits a radial orientation of the latching unit.

Furthermore, the invention also comprises the use of the locking unit ina parking lock of an automatic transmission. However, this is not thesole application of the proposed locking unit. It can be used whereverthe position of a component moving axially, i.e. parallel to itslongitudinal extent, is to be defined, i.e. is to be locked.

In this connection, it is emphasized in particular that all of thefeatures and properties, but also procedures described with respect tothe device can expediently also be transferred in respect of thedrafting of the method according to the invention and can be used withinthe meaning of the invention and are considered to also be disclosed.The same also applies in the opposite direction, that is to say featureswhich are structural, i.e. are according to the device, that arementioned only with regard to the method can also be taken intoconsideration and claimed within the scope of the device claims and arelikewise included in the disclosure.

The invention is illustrated schematically in particular in a number ofexemplary embodiments in the drawing, in which:

FIG. 1a shows, in a vertical section, a first exemplary embodiment ofthe locking unit according to the invention,

FIG. 1b shows an enlarged detail in the region of the center sectionaccording to fig. la,

FIGS. 2a and 2b each show, in a vertical section, a second exemplaryembodiment of the locking unit according to the invention in twodifferent positions of the piston,

FIGS. 3a and 3b show, in a three-dimensional view (FIG. 3b ) and in avertical sectional view (FIG. 3a ), the center section according to thelocking unit according to the invention,

FIGS. 4a to 4c show possible embodiments of a fluid-tight connectionbetween housing and tube section,

FIG. 5 shows, in a vertical section, a third exemplary embodiment of thelocking unit according to the invention.

In the figures, identical or mutually corresponding elements are eachdenoted by the same reference signs and are therefore not describedagain, unless expedient. The disclosures contained in the entiredescription are expediently transferrable to identical parts with thesame reference signs or the same component designations. The positionaldetails selected in the description, e.g. top, bottom, laterally, etc.are also related to the directly described and illustrated figure andcan expediently be transferred in the event of a change in position tothe new position. Furthermore, individual features or combinations offeatures from the different exemplary embodiments shown and describedcan also be independent, inventive solutions or solutions according tothe invention.

FIG. 1a schematically shows the locking unit 1 according to theinvention in a first exemplary embodiment. The locking unit 1 has ahousing 5, at the front housing end 50 of which an opening 51 isprovided from which the front end 21 of the piston 2 protrudes.

At the housing end 52 opposite the opening 51, a solenoid 3 adjoins thehousing 5 in the axial direction. Axial direction means here either theaxis of symmetry or longitudinal axis 22 of the piston 2 or else thedirection of movement of the piston 2.

In the housing 5, the piston 2 is mounted movably in the axialdirection, in particular along its longitudinal axis 22. For themovement of the piston 2, a drive is provided here; in particular, thepiston 2 can be acted upon with pressure, preferably with hydraulicpressure, wherein the force component of said pressure is directedcounter to the direction of force of a piston spring 23. The pistonspring 23 is supported here firstly on a housing step adjoining thehousing end 50 on the inside or on a step 53 of the housing 5. Secondly,the piston spring 23 is supported on a flange ring 24 of the piston 2.Said flange ring 24 lies in the interior, centrally in the housing 5.

Owing to the pressure, the piston 2 moves between a plurality ofpositions; in the variant shown here, for example, two positions areprovided. The position of the piston 2 in the respective positions canbe secured by a latching unit 4 which is equipped with latching elements40. For the actuation of the latching unit 4, in particular for thelatching elements 40 thereof, use is made of the solenoid 3 or use ismade of the elements thereof.

The solenoid 3 has a coil body 32 which bears a winding 33. The lattercomprises a wire through which an electrical current can flow. Thewinding 33 is closed radially on the outside (with respect to thelongitudinal axis 22) by a solenoid housing 34. Energizing the winding33 gives rise to a magnetic field.

An armature space 35 is provided in the interior of the coil body 32,wherein the armature space 35 here fills approximately half of theinterior space of the coil body 32. The armature space 35 is orientedhere in the direction of the piston 2. The remaining region of theinterior space of the coil body 32 is filled by a solenoid core 36which, as customary, is composed of soft magnetic material which readilyguides the magnetic field lines. Located in the armature space 35 is anarmature 30 which, in the exemplary embodiment shown here, is designedin the manner of a cylinder and has a base surface 37. An air gap 39 isformed between the base surface 37 and an end surface 38 of the solenoidcore 36, said end surface facing the armature space 35.

If the winding 33 is not energized, a solenoid spring 300 pushes thearmature 30 to the right such that the air gap 39 is at its maximumextent. If the winding 33 is energized, it generates a magnetic fieldwhich pushes the armature 30 to the left counter to the force of thesolenoid spring 300 such that the air gap 39 is closed.

The armature 30 bears an armature rod 31. The armature rod 31 isoriented here concentrically with respect to the armature 30, andarmature 30 and armature rod 31 are mounted movably in the axialdirection, i.e. parallel to the longitudinal axis 22, in the armaturespace 35. The design is selected here in such a manner that the armature30 has an axial bore 301 which receives the armature rod 31. Thearmature rod 31 protrudes over the armature 30 on both sides thereof.

An axial bore 302 is likewise provided in the solenoid core 36. Thearrangement is selected in such a manner that a mounting for thearmature rod 31 is located in said axial bore 302.

The armature space 35 is limited on the one side by the solenoid core36, wherein the solenoid core 36, as already described, fills that partof the interior space of the coil body 32 which faces away from thepiston 2 and thus also describes the axial end of the solenoid 3, butalso of the locking unit 1, together with the solenoid housing 34. Onthe other side, facing the piston 2, the armature space 35 is limited bya yoke part 41 which is configured in the manner of a cup and ispreferably formed from soft magnetic material in order to readily guidethe magnetic field lines. Part of the armature 30 dips here into theyoke part 41 which is configured in the manner of a cup.

The yoke part 41 here is part of the latching unit 4. The yoke part 41has a penetration bore 47 which receives and optionally also supportsthe armature rod 31.

The latching unit 4 is substantially H-shaped, as seen in section. Theradially oriented web of the H forms the yoke part 41. This is adjoinedby a first axial portion 48 and a second axial portion 49. The two axialportions 48, 49 of the H adjoining here on both sides of the web differin size or differ in length, wherein the portion 49 facing the armaturespace 35 is significantly shorter axially than the portion 48 facing thepiston 2. The larger portion 48 here or in typical embodiments isapprox. 2 to 3, 3.5 or 4 times larger or longer than the smaller portion49.

An equalizing opening 405 running radially (with respect to thelongitudinal axis 22) is arranged in the foot region of the sleeve-likefirst axial portion 48, said foot region facing the yoke part 41. Saidequalizing opening 405 fluidically connects an interior space 42 to anexterior space 406 in which a piston thrust piece 26 of the piston 2moves axially. Pressure equalization between the interior space 42 andthe exterior space 406 is possible through the equalizing opening 405.

The two portions 48, 49 radially close one corresponding receiving spaceeach. In this case, the smaller second portion 49 delimits the armaturespace 35 (this is the cup-like yoke part 41) and the larger portion 48delimits the interior space 42. The interior space 42 extends here inthe axial direction. The interior space 42 is also provided with thesolenoid spring 300 which is supported firstly on the upper side of theyoke part 41, said upper side facing the second portion 49, and secondlyon a control element 43 which is arranged on the end side of thearmature rod 31. The control element 43 is arranged here in apositionally fixed manner on the armature rod 31.

The control element 43 also has a receiving bore 401 into which thearmature rod 31 is inserted. The control element 43 is compressed in asuitable manner with the armature rod 31 and thus held in a positionallyprecise manner on the latter. The control element 43 essentiallyconsists of two different geometrical bodies, a cylinder portion and acone portion, wherein the lateral surface of the cone portion forms acone surface 400. A lateral surface 403 of the cylinder portion of thecontrol element 43 is guided, optionally also mounted, on an interiorspace wall 402 radially bounding the interior space 42. Located at theaxial end of the control element 43, the axial end facing the solenoid3, is an annular recess 404 in which the end of the solenoid spring 300is located and is thus reliably guided and held. The cone surface 400 islocated at that end of the control element 43 which lies opposite therecess 404.

It is clear that other designs are also possible for the configurationof the control element 43. For example, it is thus also conceivable thatthe cone surface is arranged on the control element on the side facingthe solenoid 3 and then the manner of functioning of the locking unit 1is optionally changed. The variant shown in FIG. 1a is planned in such amanner that, when the solenoid is currentless, i.e. when the winding 33is currentless, the control element forces the latching elements 40,which are designed here as balls, radially outward and thus blocks thepiston 2. However, the movement of the piston 2 can also be blocked whenthe solenoid 3 is energized.

The position of the air gap 39 is also variable in this case accordingto the proposal. In the exemplary embodiment shown in FIG. 1a , the airgap 39 is located on that side of the armature 30 which faces away fromthe latching unit 4, i.e. between armature 30 and the solenoid core 36.As an alternative thereto, it is also possible for the air gap then tobe formed between the armature 30 and the yoke part 41, i.e. that sideof the armature 30 which faces the latching unit 4.

The arrangement of the solenoid spring 300 in the interior space 42 isadvantageous since said elements therefore do not impair the magneticcircuit which is formed in the elements around the armature space 35.

Alternatively, an arrangement of the solenoid spring in the armaturespace or else outside the latching unit 4 is also possible in order toform a corresponding force accumulator.

When the winding 33 is energized, the air gap 39 is closed by thearmature 30 being offset to the left, as a result of which the armaturerod 31 and the control element 43 carried by the armature rod 31 arealso offset to the left, and therefore the solenoid spring 300 iscompressed and thus forms a force accumulator for a resetting movementof the unit of armature 30, armature rod 31 and control element 43 whenthe energizing of the winding 33 is switched off.

The larger first portion 48 of the latching unit 4 bears, at its end orend region 44 facing away from the yoke part 41, the latching element orthe latching elements 40 which are designed here as balls. The largerportion 48 (at least in the end region 44) is formed here in the mannerof a sleeve or cylinder. The latching elements 40 are provided as balls40 in a ball cage. The sleeve- or cylinder-like end region 44 of theportion 48 has bores 45 oriented here radially (with respect to thelongitudinal axis 22) for receiving the latching elements 40 or balls.

Depending on the axial position of the control element 43, it ispossible for the latching elements 40 or balls 40 to be able to yieldradially inwards or not.

In the exemplary embodiment shown in FIG. 1a , the piston 2 consists oftwo individual parts. The piston 2 comprises a piston tube 25 whichpartially protrudes out of the opening 51, and a piston thrust piece 26produced separately from said piston tube. The arrangement is selectedhere in such a manner that the piston thrust piece 26 adjoins the innerend of the piston tube 25 in the housing 5.

The piston tube 25 is completely hollow on the inside. It is preferablyformed as a deep drawn part, for example from metal, such as, forexample, tool steel or similar, and therefore the production of such anelement is made considerably less expensive. The wall thickness of thepiston tube 25 is therefore here also only approx. 5 to approx. 15percent of the diameter of the piston tube 25 or of the outside diameterof individual parts (e.g. inner end 27, first tube center section 29,second tube center section 202 and connecting region 203) of the pistontube 25.

The piston tube 25 lies with its flange ring 24 provided on the end sideagainst the piston thrust piece 26. The flange ring 24 therefore forms aboundary surface of the piston tube 25, said boundary surface beingoriented radially (with respect to the longitudinal axis 22). Said innerend 27 which also includes the flange ring 24 is plugged onto theconnecting ring 28 which closes off the piston thrust piece 26 in thedirection of the piston tube 25. A relatively precise fit can beprovided here and, for example, the piston tube 25 can thereby bepressed onto the piston thrust piece 26. Of course, other connectingmethods, such as, for example, welding, soldering or else adhesivebonding of the elements—piston tube 25 and piston thrust piece 26—arealternatively also possible.

The end 27 then merges in a tapering 200 into a first tube centersection 29, i.e. the diameter of the piston tube 25 in the region of thefirst tube center piece 29 is smaller than in the region of the end 27.The first tube center piece 29 then adjoins the second tube centersection 202 at a further, second tapering 201 which is designed as astep. The diameter of the piston tube 25 in the region of the secondtube center section 202 is smaller than in the region of the first tubecenter section 29. Said second tapering 201 forms a stop.

The piston 2 is guided in a plain bearing 54. The latter has an innerflange 55. If the piston 2 is displaced to the right, the movement isthereby limited by the fact that the shoulder-like tapering 201 lies onthe radially acting inner flange 55 of the plain bearing 54. Such astate is illustrated, for example, in FIG. 2 b.

The plain bearing 54 which has just been mentioned for the piston tube25 is provided on the inner side of the opening 51 of the housing 5. Thesecond tube center section 202 is mounted on said plain bearing 54. Theplain bearing 54 has an inner flange 55 which is oriented into thehousing interior and also forms the step 53 in this region. Since thehousing 5 is preferably composed of plastic, this part iscorrespondingly oversprayed. However, it is also possible for the plainbearing 54 to be inserted into a separately produced, for examplesprayed, housing 5, such as, for example, a plastics housing. Relativelyhigh accuracy is preferably favorable here, i.e. in the region of theopening 51 and of the embedding of the plain bearing 54 in the housing5.

In the position shown here of the locking unit 1, the piston 2 is pushedcompletely into the housing 5 and only the end-side connecting region203 of the piston 2 protrudes out of the housing 5. Further elements,not shown here, which are moved or held by the piston 2 are connected tothe piston 2 in the connecting region 203. The second tube centersection 202 merges here in the third tapering 204 into the connectingregion 203.

As already explained, all of the axial portions, i.e. the inner end 27,the first tapering 200, the first tube center section 29, the secondtapering 201, the second tube center section 202, the third tapering 204and the connecting region 203 are hollow on the inside.

It should be noted that the connecting region 203 has a recess providedon the center plane, i.e. is slotted. A fork-like structure of theconnecting region 203 is formed, wherein remaining half shells 211 ofthe connecting region 203 nevertheless provide sufficient stability forthe connection to a further element, not illustrated specifically. Inorder to receive a fastening bolt or similar, a respective bore or otherpenetration opening 210 is provided in the half shell 211.

The piston thrust piece 26 is likewise formed substantially in themanner of a sleeve, i.e. hollow on the inside. Its outer surface 205 isused for guidance. At the front end facing the piston tube 25, an outerring 206 is provided on the piston thrust piece 26. The outer surface ofsaid outer ring is mounted, but at least guided, on a housing inner wall56. The outer ring 206 lies in the axial direction (with respect to thelongitudinal axis 22) against the flange ring 24 of the piston tube 25.A pressure side 207 of the outer ring 206, which pressure side facesaway from the flange ring 24, is acted upon with pressure, preferablywith hydraulic pressure, and is therefore also of correspondingly soliddesign. An annular pressure space 70 is provided here.

The piston thrust piece 26 is therefore preferably realized as a turnedpart. It is preferably composed of tool steel. An encircling step 208which receives an O ring seal or a sealing ring 209 is provided radiallyon the outside of the pressure side 207. Since said O ring seal or thesealing ring 209 is exposed to the hydraulic pressure, it is alsopressed in the radial direction and thus reliably closes a gap whichperhaps still remains between the radial outer surface of the outer ring206 and the housing inner wall 56.

Furthermore, a center section 6 is provided. The center section 6 islikewise designed in the manner of a sleeve and its inner side forms abearing surface 60 for the piston thrust piece 26. The bearing surface60 interacts here with the lateral surface or outer surface 205 of thepiston thrust piece 26. The center section 6 is positionally fixed inthe locking unit 1. For example, the center section 6 is provided as aturned part and is preferably composed of a customary tool steel. In afurther preferred refinement, it is provided that the center section 6is designed as a sintered shaped part or is manufactured in a formativemethod, in particular by means of 3D printing, metal powder injectionmolding, selective laser melting or selective laser sintering. Sinteringor formative manufacturing are cost-effective production methods withwhich in addition workpieces shaped virtually as desired can be producedin a single working cycle.

The center section 6 has an axial length (with respect to thelongitudinal axis 26) depending on other components of the proposedlocking unit 1.

The axial length of the center section 6 corresponds here to approx.100-200%, preferably approx. 130-170%, of the stroke of the piston 2.

The axial length of the center section 6 corresponds here to approx.20-50%, preferably approx. 30-40%, of the axial length of the piston 2.

The axial length of the center section 6 corresponds here to approx.10-30%, preferably approx. 13-20%, of the axial length of the lockingunit 1.

The outer surface 205 here is the lateral surface of a cylinder. Theouter surface 205 bears a further O ring seal 213 in a circumferentialgroove 212 at its end facing away from the piston tube 25 and facing thesolenoid 3. Said O ring seal 213 seals the gap which remains between theouter surface 205 and the bearing surface 60 and is pressurized, in thedirection of the solenoid 3.

The piston 2 shown in FIG. 1a consists of the two components, the pistontube 25 and the piston thrust piece 26, which are fixedly connectedmechanically to each other in the variant shown here because, forexample, they are plugged on or compressed. However, they canalternatively also be formed in a floating manner with respect to eachother, i.e. can be pressed against each other only because of thedynamic effect of the applied pressure, on the one hand, and thecounter-directed force of the piston spring 23, on the other hand.

Said piston 2 which consists of two components is first of all mountedon the bearing surface 60 of the center section 6 by means of the pistonthrust piece 26. A further mounting is alternatively provided on theouter ring 206 of the piston thrust piece 26 in cooperation with thehousing inner wall 56. Ultimately, the second tube center section 202 ofthe piston tube 25 is mounted on the plain bearing 54 provided on oneside.

An inner surface 214 of the piston thrust piece 26 is also not smooth,but rather has indentations or latching receptacles 20, 20 a, 20 b onthe end side in each case, i.e. spaced apart axially from one another(with respect to the longitudinal axis 22). The diameter of thering-like indentations or latching receptacles 20, 20 a, 20 b is largerhere than the diameter of the inner surface 214 lying between them.

The latching receptacles 20, 20 a, 20 b are turned into the innersurface 214 of the sleeve-like piston thrust piece 26 in the form of astep or inner shoulder. The latching unit 4 is arranged in the housing 5in a positionally fixed manner, and the piston 2 is designed to beaxially or longitudinally movable in relation to the latching unit 4.However, in the position shown in FIG. 1 a, the movement of the piston 2to the right, in the direction of the opening 51, is blocked by thelatching unit 4; the locking unit 1 is blocked in the retracted positionof the piston 2.

As already mentioned, the latching unit 4 has latching elements 40,here, for example, balls 40 of a ball cage, which are mounted inrespective bores 45 so as to be movable radially (with respect to thelongitudinal axis 22). The solenoid 3 is shown in a dropped position,i.e. the winding 33 is not acted upon with current. The air gap 39 istherefore formed between the armature 30 and the solenoid core 36 sincethe solenoid spring 300 offsets the armature 30 to the right andtherefore also the control element 43 on which the solenoid spring 300is indeed supported. The control element 43 therefore passes onto theaxial position of the latching elements/balls 40, and therefore the conesurface 400 of the control element 43 acts on the latchingelements/balls 40 and pushes the latter radially outwards (with respectto the longitudinal axis 22) into the respective latching receptacles20, 20 a. Then, however, a longitudinal movement of the piston 2, i.e. amovement of the piston 2 to the right, is blocked since a first innershoulder 215 a which bounds the latching receptacle 20, 20 a liesagainst the latching elements 40 which are offset radially outward. Thefirst inner shoulder 215 a is located here on the first latchingreceptacle 20 a, on the side facing the second latching receptacle 20 b.

In the position shown in FIG. 1 a, that end of the piston thrust piece26 which faces away from the piston tube 25 furthermore lies against aradially running stop surface 61 of the center section 6 and thus alsoblocks a movement of the piston 2 to the left, in the direction of thesolenoid 3.

For the sake of completeness, reference should also be made at thisjuncture to FIG. 2b which shows the position in which the piston 2 isextended to the right completely out of the housing 5. This end positionis firstly limited by the second tapering 201 lying against the innerflange 55 of the plain bearing 54 in the region of the opening 51 of thehousing 5. In this position, the solenoid 3 is in turn switched off,i.e. the winding 33 is not acted upon with current, and therefore thecontrol element 43 pushes the latching elements/balls 40 into the outeror second latching receptacle 20, 20 b of the piston thrust piece 26 andthus on the other hand blocks a movement to the left. The radiallypushed-out latching elements/balls 40 then lie against a second innershoulder 215 b which bounds the second latching receptacle 20 b. Thesecond inner shoulder 215 b is located here on that side of the secondlatching receptacle 20 b which faces the first latching receptacle 20 a.As already described, the two latching receptacles 20 a and 20 b arespaced apart from each other axially (with respect to the longitudinalaxis 22).

The piston 2, in particular the piston thrust piece 26, is mountedmovably between the latching unit 4 arranged radially on the inside andthe center section 6 arranged radially on the outside. In the embodimentshown, the center section 6 takes up a central position in the lockingunit 1. On the one hand, the radial outer side 62 of said center sectionbears the sleeve-like housing 5. However, on the other hand, it alsoproduces a connection to the solenoid 3, in particular to the solenoidhousing 34 thereof.

In the lower region in FIG. 1 b, a radially running gap 65 can be seenbetween the solenoid housing 34 and the housing 5, said gap extendingradially on the inside into a channel 66 a which is in fluidic contactwith an interspace 66 b which arises between the thrust piece 26 and thelatching unit 4. The radially running channel 66 a is realized here insuch a manner that a recess 67 (see FIGS. 3a and 3b ) is provided on afoot region 68 (see FIGS. 3a and 3b ) of the center section 6, the footregion facing the solenoid 3, and therefore the foot region 68 of thecenter section 6, said foot region facing the solenoid 3, does not lieover the entire extent against the flange part of the coil body 32. Thefluidically interconnecting elements of interspace 66 b, channel 66 aand gap 65 permit venting of the interior of the locking unit 1.

Furthermore, the center section 6 orients the solenoid 3 radially withrespect to the latching unit 4. It is favorable to realize a high degreeof concentricity in this region.

The center section 6, on its side facing away from the solenoid 3 orfacing the piston tube 25, has an encircling contact shoulder 63 whichis then adjoined by an annular and/or conical connecting region 64. Saidconnecting region 64 is a constituent part of the center section 6. Theproposal according to the invention is highly variable for theconfiguration of the connecting region 64. The connecting region 64 herehas a plurality of tasks.

First of all, said connecting region supports a tube section 57 whichmay also be referred to as a sleeve section, which is part of thehousing 5 and the inner side of which provides the housing inner wall56. Furthermore, at least part of the connecting region 64 limits thepressure space 70, i.e. is in contact with the pressurizable medium. Forthis purpose, the tube section 57 is pushed or pressed onto thepreferably annular region of the connecting region 64. As alreadydescribed, the piston 2, in particular the piston thrust piece 26, liesagainst the housing inner wall 56; in this respect, the tube section 57has the properties of a cylinder. The tube section 57 preferably limitsor conducts the pressure not only on its housing inner wall 56, but alsoon its tube outer side 58.

The mounting of the first end piece of the tube section 57 on the centersection 6 underlines the central importance of the center section 6 inthe embodiment shown here. The second end piece of the tube section 57is mounted in the housing 5, and the inner side of the tube section 57serves as a mounting or guide of the piston 2.

In the present embodiment, the tube section 57 is connected in afluid-tight manner to the housing 5 on the right side. This is broughtabout by the fact that the tube section 57 is pushed into a groove 80 ofthe housing 5. The groove 80 is of annular design here and is limitedradially on the inner side by a projection 81 of the housing 5. It isensured by means of the connection of fluid-tight design that fluidwhich is under pressure and which is located in the pressure conductingchannel 71 does not pass at the connecting point between housing 5 andtube section 57 into a region radially on the outer side of the pistontube 25, which would counteract a movement of the piston 2 to the right,which is intended to be achieved specifically by means of the fluidunder pressure, as described below. Possible embodiments of a tightconnection are illustrated in FIGS. 4a to 4c and will be describedfurther below.

A pressure connection, not illustrated specifically in FIG. 1 a, whichprovides a pressurized medium as the drive for the piston 2 is locatedon the housing 5. Said pressure connection is preferably arranged inthat half of the housing 5 which faces the opening 51; in particular, itis situated close, in particular very close, to the opening 51. In ordernow to realize as large a stroke of the piston 2 as possible, thepressure side 207, which can be acted upon with pressure, of the pistonthrust piece 26 has to be removed as far as possible from the opening 51in the retracted position of the piston 2. This boundary condition leadsto the pressurized medium first of all having to be conducted in thehousing 5 or in the locking unit 1 counter to the preferred direction ofmovement (the working movement realized by the pressurization, to theright in FIG. 1a ) of the piston 2 in order then to be deflected at asuitable point and guided onto the pressure side 207.

The pressure connection, not shown, is therefore fluidically connectedto the pressure conducting channel 71 running substantially axially(with respect to the longitudinal axis 22). Said pressure conductingchannel 71 is limited radially on the inside by the outer side 58 of thetube section 57 and radially on the outside by the plastics housing 5,in particular the inner wall 500 thereof. The pressure conductingchannel 71 can surround the entire tube section 57 (with respect to itscircumferential direction) or can extend axially only in one segment, asshown in FIG. 1 a.

Since the tube section 57 according to one embodiment is pluggedfixedly, and therefore also tightly or in a pressure-tight manner on theconnecting region 64 of the center section 6, an aperture 501 isprovided at the axial height, with respect to the longitudinal axis 22,of the connecting region 64 in the tube section 57, through whichaperture the pressurized medium passes out of the pressure conductingchannel 71 into the pressure space 70 on the inner side of the tubesection 57.

The tube section 57 therefore has a plurality of tasks.

Its housing inner wall 56 serves as a guide or mounting of the piston 2.Its outer side 58 serves at least partially as the pressure conductingchannel 71.

Furthermore, the tube section 57 supports or reinforces the housing 5which is preferably composed of plastic. This combined construction ofthe housing 5 combines a low mass and favorable production with a highdegree of wear resistance and therefore with high availability of alocking unit configured in such a manner.

The end 59 of the tube section 57 that faces away from the connectingregion 64 is surrounded annularly by the plastics material of thehousing 5. The pressure conducting channel 71 therefore does notinevitably extend over the entire axial length of the tube section 57.For example, the tube section 57 can be insert molded by the plastic ofthe housing 5; alternatively, for example, the tube section 57 can beplugged or pressed into a housing 5 produced in a separate manufacturingstep.

FIGS. 3a, 3b show an exemplary embodiment of the center section 6. Acenter section 6 configured in such a manner is also found in the useexample according to FIG. 2a or 2 b.

The center section 6 is formed in the manner of a sleeve. In theinstalled state, it has a foot region 68 which faces the solenoid 3 andis adjoined by a center portion 69. On the side facing away from thefoot region 68, the center section 6 is closed by a connecting region64. The center portion 69 has the largest diameter and, in the installedstate, lies directly against the plastics material of the housing 5.

The diameter of the foot region 68 is smaller than the diameter of thecenter portion 69. The foot region 68 is not completely configured as anencircling ring, but rather has, in a certain angular segment, a recess67 which, in the installed state, forms the channel 66 a. The centerportion 69 merges with the radially running contact shoulder 63 into theconnecting region 64.

The outside diameter of the connecting region 64 is also smaller thanthe diameter of the center portion 69. The tube section 57 is pluggedonto the connecting region 64 in the installed state. For this purpose,the connecting region 64 is provided with a multiplicity of supportingsegments 600 which are designed as lateral segments on the cylinder-likeouter surface of the connecting region 64 and are each separated bysegment interspaces 72. Said segment interspaces 72 are formed asclearances in the lateral surface of the connecting region 64 and guidethe medium; that is to say, in the installed state and during operation,the corresponding operating pressure prevails in the segment interspaces72. The segment interspaces 72 are therefore part of the media-guidingsystem.

The exemplary embodiment of the center section 6 according to FIGS. 1aor 1 b differs with respect thereto as follows:

As already explained, there is a fluidic connection between the pressureconducting channel 71, which is arranged on the radial outer side of thetube section 57, and the pressure space 70, which is arranged on theradial inner side of the tube section 57. In the example shown in FIGS.1a and 1 b, said connection is realized by the aperture 501 in the tubesection 57. That end 502 of the tube section 57 which faces the centersection 6 is pushed here completely onto the connecting region 64 andlies fully (and therefore also in a sealing manner) against the radiallyoutwardly running contact shoulder 63.

FIGS. 2a and 2b show the use of the center section 6 according to FIGS.3a and 3b . It can readily be seen that the end 502 facing the centersection 6 is spaced apart axially (with respect to the longitudinal axis22) from the contact shoulder 63. The segment interspaces 72 extendingin the axial direction (with respect to the longitudinal axis 22) aretherefore fluidically connected to the pressure conducting channel 71and also to the pressure space 70. The axial distance (with respect tothe longitudinal axis 22) of the tube end 502 from the contact shoulder63 corresponds here to the aperture 501 and here forms a radialconnection from the inner side of the tube section 57 to the outer sideof the tube section 57. This connection runs here outside the tubesection 57, i.e. offset axially outward, with respect to the tubesection end 502.

FIGS. 2a and 2b each show, in a vertical section, a second exemplaryembodiment of the locking unit 1 according to the invention in twodifferent positions of the piston.

In FIG. 2a , the piston 2 is completely retracted in the locking unit 1and is secured in said end position by the latching unit 4. Thecompletely retracted position of the piston 2 results from the fact thatthe piston thrust piece 26 is exposed only to a small pressure, if anypressure, which generates a force which is smaller than the oppositespring force of the piston spring 23. In FIG. 2b , the piston 2 iscompletely pushed out of the locking unit 1 and is likewise secured insaid end position by the latching unit 4.

As already explained, the blocking position of the latching unit 4 isrealized in the dropped, i.e. non-energized, state of the solenoid 3,but without the invention being set thereto; the blocking position canalternatively also be realized in the energized state of the solenoid.

In order, for example, now to move the piston 2 from the position shownin FIG. 2a into the position shown in FIG. 2b , the procedure can be asfollows.

-   -   First of all, the blockage of the latching unit 4 should be        eliminated. This takes place by the solenoid 3 being energized        and, as a result, the unit of armature 30, armature rod 31 and        control element 43 being offset axially and thus permitting        radial movability of the latching elements/balls 40 which can        then, for example, yield back radially inward and thus permit        the axial movement (all with respect to the longitudinal axis        22) of the piston 2, here in particular of the piston thrust        piece 26.    -   In the next step, a drive of the piston 2, here, for example, a        hydraulic pressurization, is activated and the operating        pressure prevailing on the piston thrust piece 26 then pushes        the piston 2, consisting of the piston tube 25 and the piston        thrust piece 26, to the right counter to the force of the piston        spring 23, away from the solenoid 3. The piston tube 25 is        thereby pushed out of the opening 51.    -   The end position thus achieved of the piston 2 is then secured        again by the latching unit 4; for this purpose, the current        through the winding 33 of the solenoid 3 is switched off or is        at least so greatly reduced that the resulting magnetic force on        the armature 30 is lower than the spring force of the magnetic        fields 300 acting counter to the magnetic force. The dropping        armature 30 shifts the control element 43 axially in such a        manner that the cone surface 400 thereof pushes the latching        elements/balls 40 radially outward into the latching receptacle        20 and thus prevents the piston 2 from yielding back, for        example when pressure on the piston thrust piece 26 is switched        off.

FIGS. 4a to 4c each show a detail of the connecting point between tubesection 57 and housing 5, wherein different possibilities of thefastening and sealing are described.

As already mentioned further above, the tube section 57 is accommodatedin a groove 80 which is formed annularly and is bounded radially on theinner side by a projection 81.

In the embodiment of FIG. 4a , a seal 82 in the form of a sealing ringis arranged between housing 5 and tube section 57. Said seal ensures afluid-tight design.

In the embodiment of FIG. 4b , a seal 83 in the form of sealing materialmade of silicone, the sealing material ensuring the fluid-tight design,is arranged laterally of the tube section 57. The tube section 57 cantherefore also be held in the groove 80.

In the embodiment of FIG. 4c , a number of bores 84 are formed in thetube section, through which bores a respective engagement part 85 of thehousing 5 passes. This can take place, for example, by the fact that thehousing 5 is sprayed around the tube section 57 during manufacturing.The engagement part 85 can therefore be connected in particular in amaterial bonded manner to the rest of the housing 5 and can thereforeensure an advantageous fastening of the tube section 57.

Alternatively, it is also clear that the end of the tube section 57 canbe insert molded even without the arrangement of bores 84. For example,at least at the end of the tube section 57, the plastics material of thehousing 5 can lie here against said tube section on the inside (by meansof the projection 81) and on the outside.

FIG. 5 shows a locking unit 1 according to a third exemplary embodiment.Essentially the differences over the exemplary embodiments alreadydescribed will be discussed below. Otherwise, reference should be madeto the description which has already been provided.

As already explained in the previously described exemplary embodiments,the piston 2 is hollow, and therefore a cavity 220 is formed in thepiston 2. Said cavity is divided into a first cavity region 221 and asecond cavity region 222. The first cavity region 221 is arranged in thepiston thrust piece 26. The second cavity region 222 is arranged in thepiston tube 25.

A filter unit 500 is arranged between the first cavity region 221 andthe second cavity region 222. Said filter unit has an outer annular edge510 with which it is fastened, as shown, in the piston 2, specificallybetween piston tube 25 and piston thrust piece 26. Arranged internallywith respect to the annular portion 510 is a cup-shaped region 520, onthe end side of which a filter 530 is arranged.

The annular edge 510 and the cup-shaped region 520 ensure in particularthat the first cavity region 221 and the second cavity region 222 aresealed fluidically in relation to each other within the piston 2 apartfrom the filter 530. This prevents fluid from flowing elsewhere thanthrough the filter 530 between the two cavity regions 221, 222 and thustransporting dirt particles without filtering.

The filter 530 ensures that an exchange of fluid between the two cavityregions 221, 222 is possible, but an exchange of dirt particles isprevented. For this purpose, the filter has a multiplicity of pores, therespective size of which is selected in such a manner that fluidicexchange is possible, but dirt particles which are typically to beexpected are kept away. In particular, dirt particles which possiblypenetrate into the piston 2 from the right side of FIG. 5, i.e., forexample, originate from connected or actuated components, can thereby bekept away from the elements bringing about the latching.

It should be pointed out that, in the embodiment of FIG. 5, the centersection 6 and the latching unit 4 are formed integrally. This featureleads to particularly simple production and high stability, but isfunctionally independent of the use of a filter, as just described.

Possible features of the proposal are reproduced in structured formbelow. The features reproduced in structured form below can be combinedwith one another as desired and can be incorporated in any combinationinto the claims of the application. It is clear to a person skilled inthe art that the invention already arises from the subject matter havingthe fewest features. In particular, advantageous or possiblerefinements, but not the only possible refinements of the invention, arereproduced below.

The invention comprises:

A locking unit, in particular for the parking lock of an automatictransmission, for locking the movement of a piston (2) which is movableby a drive, and in particular can be acted upon with pressure orhydraulic pressure, the locking unit (1) having a solenoid (3) and atleast one latching element (40), and the latching element (40)interacting with the armature (30) or the armature rod (31) of thesolenoid (3), and the piston (2) having at least one latching receptacle(20, 20 a, 20 b), and the piston (2) being securable by the retaininginteraction of the latching element (40) with the latching receptacle(20, 20 a, 20 b), wherein the piston (2) is at least partially mountedin a center section (6) which is at least partially surrounded by ahousing (5), wherein the locking unit (1) has a latching unit (4) whichsupports the latching elements (40), wherein the latching unit (4) andthe center section (6) are formed integrally.

The abovementioned locking unit, wherein the center section (6) isdesigned in the manner of a sleeve.

The abovementioned locking unit, wherein an inner side of the centersection (6) forms a bearing surface for the piston (2) or for a pistonthrust piece (26) of the piston (2).

The abovementioned locking unit, wherein the center section (6) is inthe form of a turned part or sintered shape part, is produced in aformative method or is produced by means of 3D printing, metal powderinjection molding, selective laser melting or selective laser sintering.

The abovementioned locking unit, wherein the center section (6) has anaxial length of 100% to 200% or of 130% to 170% of a stroke of thepiston (2).

The abovementioned locking unit, wherein the center section (6) has anaxial length of 30% to 40% of an axial length of the piston (2).

The abovementioned locking unit, wherein the center section (6) has anaxial length of 13% to 20% of an axial length of the locking unit (1).

The abovementioned locking unit, wherein the piston (2) is hollow on theinside completely along its axial extent.

The abovementioned locking unit, wherein the piston (2) has a cavitywhich extends axially through the entire piston (2).

The abovementioned locking unit, wherein the cavity is open at bothaxial ends.

The abovementioned locking unit, wherein the cavity continuously or insections has a wall which is thinner than a quarter of a diameter of thepiston (2) or is thinner than a tenth of the diameter of the piston (2).

The abovementioned locking unit, wherein the piston (2) has a completelyhollow piston tube (25) along an axial portion and a piston thrust piece(26), which is connected to the piston tube (25), along a further axialportion.

The abovementioned locking unit, wherein the latching receptacles (20,20 a, 20 b) are formed in the piston thrust piece (26).

The abovementioned locking unit, wherein the piston tube (25) is in theform of a deep drawn part, from tool steel or from metal.

The abovementioned locking unit, wherein the piston tube (25) has a wallthickness of 5% to 15% of the diameter of the piston tube (25).

The abovementioned locking unit, wherein the piston (2) is at leastpartially mounted in the housing (5).

The abovementioned locking unit, wherein the housing (5) is entirely orpartially formed from plastic.

The abovementioned locking unit, wherein the piston tube (25) has a tubecenter section (29) with an outer tapering (201), wherein the tapering(201) of the piston tube (25) interacts with a step (53) formed in thehousing (5), in order to limit a movement of the piston (2) away fromthe solenoid (3).

The abovementioned locking unit, wherein a piston spring (23) isprovided between housing (5) and piston (2) and pushes the piston (2) inthe direction of the solenoid (3).

The abovementioned locking unit, wherein the piston (2) is mountedopposite the solenoid (3) in a plain bearing (54) of the housing (5).

The abovementioned locking unit, wherein the housing (5) has an internaltube section (57), wherein a pressure conducting channel (71) is formedon the outer side of the tube section (57).

The abovementioned locking unit, wherein the pressure conducting channel(71) is connectable hydraulically from the outside via a connectionthrough the housing (5).

The abovementioned locking unit, wherein the center section (6) has aradial outer side (62) which supports the housing (5).

The abovementioned locking unit, wherein the center section (6) isconnected to a solenoid housing (34) of the solenoid (3).

The abovementioned locking unit, wherein the center section (6) has anencircling contact shoulder (63) on its side facing away from thesolenoid (3) and/or facing the piston tube (25), which contact shoulderis adjoined by an annular and/or conical connecting region (64).

The abovementioned locking unit, wherein the connecting region (64)supports the tube section (57).

The abovementioned locking unit, wherein a number of segment interspaces(72) are designed as notches radially on the outer side in theconnecting region (64).

The abovementioned locking unit, wherein the segment interspaces (72)are designed as a fluidic connection between pressure conducting channel(71) and a pressure space (70) within the tube section (57).

The abovementioned locking unit, wherein respective supporting segments(600) which support the tube section (57) are formed between the segmentinterspaces (72).

The abovementioned locking unit, wherein the connecting region (64) isdesigned as a crown ring.

The abovementioned locking unit, wherein the latching unit (4) has aportion (49) facing the solenoid (3) or an armature space (35) of thesolenoid (3) and a portion (48) facing the piston (2), which portionsare each of sleeve-shaped design.

The abovementioned locking unit, wherein that portion (49) of thelatching unit (4) which faces the solenoid (3) partially accommodatesthe armature (30) in at least one end position.

The abovementioned locking unit, wherein an interior space (42) which isopen on the piston side is formed in the latching unit (4) or in thatportion (48) of the latching unit (4) which faces the piston (2).

The abovementioned locking unit, wherein an exterior space (406) isformed between latching unit (4) and housing (5) or between latchingunit (4) and center section (6).

The abovementioned locking unit, wherein exterior space (406) andinterior space (42) are fluidically connected via an equalizing opening(405) formed in the latching unit (4).

The abovementioned locking unit, wherein the exterior space (406) isvented by a channel (66 a) which is formed in or on the center section(6).

The abovementioned locking unit, wherein the latching unit (4) isfixedly connected directly or indirectly to the housing (5).

The abovementioned locking unit, wherein a control element (43) which isfixedly connected to the armature rod (31) is arranged in the latchingunit (4).

The abovementioned locking unit, wherein the control element (43) is atleast partially movable within the portion (48) facing the piston (2).

The abovementioned locking unit, wherein a number of radial bores (45)for receiving the latching elements (40) are formed in the latching unit(4).

The abovementioned locking unit, wherein the latching elements (40) areof spherical design.

The abovementioned locking unit, wherein the control element (43) isdesigned in order, at least in one position, to push the latchingelements (40) radially outward.

The abovementioned locking unit, wherein the latching elements (40),when they are pushed radially outward, come into engagement with one ofthe latching receptacles (20, 20 a, 20 b).

The abovementioned locking unit, wherein the piston (2) has at least twolatching receptacles (20 a, 20 b) which are spaced apart axially fromone another.

The abovementioned locking unit, wherein the piston (2) is lockable intwo different positions by means of the two latching receptacles (20 a,20 b).

The abovementioned locking unit, wherein the solenoid (3) has a solenoidcore (36) which is arranged at one axial end of the locking device (1).

The abovementioned locking unit, wherein the armature rod (31) is guidedin a bore of the solenoid core (36).

The abovementioned locking unit, wherein the piston (2) has a connectingregion (203) which is on the end side axially and protrudes from thehousing (5) even in the completely retracted state of the piston (2).

The abovementioned locking unit, wherein the connecting region (203) isdesigned in the manner of a fork.

The abovementioned locking unit, wherein the connecting region (203) isdesigned as a punched-out fork head.

The abovementioned locking unit, wherein the piston (2) or the pistonthrust piece (26) is at least partially arranged radially betweenlatching unit (4) and housing (5) or is arranged between latching unit(4) and center section (6).

The abovementioned locking unit, wherein the solenoid has a winding (31)for generating a magnetic field for moving the armature (30) and/or thearmature rod (31).

The abovementioned locking unit, wherein the inner tube section (57) isdesigned as a guide of the piston (2).

The abovementioned locking unit, wherein the pressure conducting channel(71) is limited at least partially radially, with respect to thelongitudinal axis (22) of the piston (2), on the inside by the outerside of the tube section (57) and on the outside by the inner wall (500)of the housing (5).

The abovementioned locking unit, wherein the tube section (57) isconnected to the housing (5) or is part of the housing (5).

The abovementioned locking unit, wherein the piston (2) lies against thetube section (57).

The abovementioned locking unit, wherein the piston (2) slides along thetube section (57).

The abovementioned locking unit, wherein the piston (2) lies in afluid-tight manner against the tube section (57).

The abovementioned locking unit, wherein the piston (2) has a sealingmeans which seals the piston (2) on the tube section (57) in afluid-tight manner.

The abovementioned locking unit, wherein the sealing means is a sealingring (209) or an O ring.

The abovementioned locking unit, wherein the sealing ring (209) or the Oring is provided in an encircling step (208) of the piston (2).

The abovementioned locking unit, wherein the sealing ring (209) or the Oring is provided in a piston thrust piece (26) of the piston (2).

The abovementioned locking unit, wherein the inner side of the tubesection (57) forms a housing inner wall (56) against which the piston(2) lies.

The abovementioned locking unit, wherein the tube section (57) is ofrectilinear and/or cylindrical design at least along a portion on whichthe piston (2) is guided.

The abovementioned locking unit, wherein the tube section (57) is formedfrom metal or from plastic.

The abovementioned locking unit, wherein the center section (6) isdesigned in the axial direction, with respect to the longitudinal axis(22) of the piston (2), to be shorter on the piston side than thelatching unit (4) and in particular the radial bores (45) of thelatching unit (4) are not concealed in the radial direction, withrespect to the longitudinal axis (22) of the piston (2), by the centersection (6).

The abovementioned locking unit, wherein the inner tube section (57) isconnected in a fluid-tight manner to the housing (5).

The abovementioned locking unit, wherein the tube section (57) isaccommodated in a groove (80) of the housing (5).

The abovementioned locking unit, wherein the groove (80) of the housing(5) is of annular design.

The abovementioned locking unit, wherein a seal (82, 83) is arrangedbetween housing (5) and tube section (57).

The abovementioned locking unit, wherein the seal (82, 83) is arrangedin the groove (80).

The abovementioned locking unit, wherein the seal (82) is an O ring orsealing ring.

The abovementioned locking unit, wherein the seal (83) is a sealingmaterial or a silicone sealing material.

The abovementioned locking unit, wherein a number of bores (84) in whichengagement parts (85) of the housing (5) engage is formed in the tubesection (57).

The abovementioned locking unit, wherein the housing (5) has an inparticular annular projection (81) which partially engages around thetube section (57).

The abovementioned locking unit, wherein the projection (81) limits thegroove (80) radially on the inside.

The abovementioned locking unit, wherein the tube section (57) isconnected to the housing (5) in a gas-tight and/or pressure-tightmanner.

The abovementioned locking unit, wherein the housing (5) supports thetube section (57).

A method for producing a locking unit as described above, wherein thetube section is provided and the housing is insert molded around thetube section.

The abovementioned method, wherein a groove into which the tube sectionis subsequently introduced is formed in the housing.

The abovementioned method, wherein a number of bores is formed in thetube section, wherein a number of engagement parts which each engage ina bore has been formed or is formed in the housing.

The claims which are filed at this point with the application and claimsfiled later are without prejudice to the purpose of achieving furtherprotection.

Should it be found here upon closer examination, in particular also ofthe relevant prior art, that one feature or another, althoughadvantageous, is not absolutely imperative in relation to the aim of theinvention, then, of course, the attempt will be made to achieve awording which no longer has such a feature, in particular in the mainclaim. Such a sub-combination is also covered by the disclosure of thisapplication.

It should also be noted that the refinements and variants of theinvention that are described in the various embodiments and shown in thefigures can be combined with one another in any desired manner. It ispossible for individual features, or a number of features, to beinterchanged as desired. These combinations of features are likewisedisclosed here.

The dependency references given in the dependent claims relate to thefurther development of the subject matter of the main claim by means ofthe features of the respective dependent claim. However, these shouldnot be understood as obviating the need to achieve independentsubstantive protection for the features of the appended dependentclaims.

Features which have been disclosed only in the description, or alsoindividual features from the claims which comprise a number of features,can at any time be adopted in the independent claim/claims as being ofimportance which is essential for the purpose of distinguishing theinvention from the prior art, to be precise even when such features havebeen mentioned in conjunction with other features or achieveparticularly advantageous results in conjunction with other features.

1. A locking unit, in particular for the parking lock of an automatictransmission, for locking the movement of a piston (2) which is movableby a drive and in particular can be acted upon with pressure orhydraulic pressure, the locking unit (1) having a solenoid (3) and atleast one latching element (40), and the latching element (40)interacting with the armature (30) or the armature rod (31) of thesolenoid (3), and the piston (2) having at least one latching receptacle(20, 20 a, 20 b), and the piston (2) being securable by the retaininginteraction of the latching element (40) with the latching receptacle(20, 20 a, 20 b), wherein the piston (2) is at least partially mountedin a center section (6) which is at least partially surrounded by ahousing (5).
 2. The locking unit as claimed in claim 1, wherein thecenter section (6) is designed in the manner of a sleeve.
 3. The lockingunit as claimed in either of the preceding claims, wherein an inner sideof the center section (6) forms a bearing surface for the piston (2) orfor a piston thrust piece (26) of the piston (2).
 4. The locking unit asclaimed in one of the preceding claims, wherein the center section (6)is in the form of a turned part or sintered shaped part, is produced ina formative method or is produced by means of 3D printing, metal powderinjection molding, selective laser melting or selective laser sintering.5. The locking unit as claimed in one of the preceding claims, whereinthe center section (6) has an axial length of 100% to 200% or of 130% to170% of a stroke of the piston (2); the center section (6) has an axiallength of 30% to 40% of an axial length of the piston (2); and/or thecenter section (6) has an axial length of 13% to 20% of an axial lengthof the locking unit (1).
 6. The locking unit as claimed in one of thepreceding claims, wherein the center section (6) has a radial outer side(62) which supports the housing (5).
 7. The locking unit as claimed inone of the preceding claims, wherein the center section (6) is connectedto a solenoid housing (34) of the solenoid (3).
 8. The locking unit asclaimed in one of the preceding claims, wherein the center section (6)has an encircling contact shoulder (63) on its side facing away from thesolenoid (3) and/or facing a piston tube (25) of the piston (2), whichcontact shoulder (63) is adjoined by an annular and/or conicalconnecting region (64) which supports the tube section (57).
 9. Thelocking unit as claimed in one of the preceding claims, wherein a numberof segment interspaces (72) as notches are formed in the connectingregion (64), radially on the outer side, said segment interspaces (72)being designed as a fluidic connection between pressure conductingchannel (71) and a pressure space (70) within a tube section (57). 10.The locking unit as claimed in one of the preceding claims, wherein theconnecting region (64) is designed as a crown ring and/or the connectingregion (64) supports the tube section (57).